Re: [mpls] [spring] to progress draft-cheng-spring-mpls-path-segment

Hi Greg,

I am not sure if the question has been answered. I would think GAL is at
the bottom of the label stack.

Thanks,
Rakesh

On Sat, Feb 16, 2019 at 4:24 PM Greg Mirsky <gregimirsky@gmail.com> wrote:

> Hi Weiqiang Cheng,
> thank you for your expedient response to my questions. The document states
> that one of the use cases for the Path segment is to be used as a
> performance, packet loss and/or delay, measurement session identifier. I
> think that RFC 6374 is the most suitable for PM OAM in SR-MPLS environment.
> Of course, the type of the encapsulated message can be identified using the
> destination UDP port number with IP/UDP encapsulation. But another option
> is to use G-ACh encapsulation. That would require the use of GAL. And that
> is how I've arrived at my original question (I should have explained it
> better, my apologies):
>
> How the Path segment and GAL are placed relative to each other in the
> SR-MPLS label stack?
>
> Regards,
> Greg
>
> On Fri, Feb 15, 2019 at 4:40 PM Weiqiang Cheng <
> chengweiqiang@chinamobile.com> wrote:
>
>> Hi Greg,
>>
>> Thanks a lot for your comments.
>>
>> My comments are in-line.
>>
>>
>>
>> B.R.
>>
>> Weiqiang Cheng
>>
>>
>>
>> *发件人:* Greg Mirsky [mailto:gregimirsky@gmail.com]
>> *发送时间:* 2019年2月15日 3:37
>> *收件人:* Alexander Vainshtein
>> *抄送:* spring@ietf.org; Stewart Bryant;
>> draft-cheng-spring-mpls-path-segment@ietf.org; mpls@ietf.org; Loa
>> Andersson
>> *主题:* Re: [spring] to progress draft-cheng-spring-mpls-path-segment
>>
>>
>>
>> Dear All,
>>
>> I concur with all what has been said in support of the adoption of this
>> draft by SPRING WG. The document is well-written, addresses the real
>> problem in SR-MPLS, and the proposed solution is technically viable.
>>
>> My comments and questions are entirely for further discussion:
>>
>>    - would the draft be expanded to demonstrate how "the Path Segment
>>    may be used to identify an SR-MPLS Policy, its Candidate-Path (CP) or a SID
>>    List (SL)"?
>>
>> [Weiqiang] Yes, It is necessary and we will add some text to demonstrate
>> this in the future version.
>>
>>    - as many use cases for the Path Segment are related to OAM
>>    operations, it would be helpful to expand on the use of GAL and the Path
>>    Segment.
>>
>>        [Weiqiang] It is always helpful to have more use cases. However,
>> The GAL is used today in MPLS-TP LSPs to flag the G-Ach and is used for OAM
>> packets only while the Path segment is used for data packets for the each
>> traffic flow. It is a little bit different.
>>
>> Regards,
>>
>> Greg
>>
>>
>>
>> On Thu, Feb 14, 2019 at 1:12 AM Alexander Vainshtein <
>> Alexander.Vainshtein@ecitele..com <Alexander.Vainshtein@ecitele.com>>
>> wrote:
>>
>> +1.
>>
>>
>>
>> I have been following this draft from its -00 revision. The current
>> revision has resolved most of the issues I (and others) have been raised
>> (e.g., elimination of excessive options).
>>
>>
>>
>> From my POV, in its current state the draft meets two basic requirements
>> for the WG adoption:
>>
>> 1.       It addresses a real and relevant problem, namely the MPLS Flow
>> Identification problem discussed in general in RFC 8372
>> <https://tools.ietf.org/html/rfc8372> and scoped to SR-MPLS LSPs in this
>> draft. Specifics of SR-MPLS include the need to provide end-to-end liveness
>> check that is one of the requirements explicitly specified in Section 2 of RFC
>> 8355 <https://tools.ietf.org/html/rfc8355>.
>>
>> 2.       It provides a reasonable (from my POV) approach to  solution of
>> this problem.
>>
>>
>>
>> I also concur with Stewart’s comment about strong similarity between the
>> approach taken in this draft for SR-MPLS and generic work in progress on
>> synonymous flow labels
>> <https://tools.ietf.org/html/draft-ietf-mpls-sfl-framework-04> that has
>> been already adopted as a MPLS WG item.  To me this is yet another
>> indication that the draft should be adopted.
>>
>>
>>
>> My 2c,
>>
>> Sasha
>>
>>
>>
>> Office: +972-39266302
>>
>> Cell:      +972-549266302
>>
>> Email:   Alexander.Vainshtein@ecitele.com
>>
>>
>>
>> -----Original Message-----
>> From: spring <spring-bounces@ietf.org> On Behalf Of Stewart Bryant
>> Sent: Wednesday, February 13, 2019 12:48 PM
>> To: Loa Andersson <loa@pi..nu <loa@pi.nu>>; spring@ietf.org;
>> draft-cheng-spring-mpls-path-segment@ietf.org
>> Subject: Re: [spring] to progress draft-cheng-spring-mpls-path-segment
>>
>>
>>
>> I have just read the draft and agree that it should be adopted by the WG.
>> It solves an important problem in instrumenting and protecting an SR path.
>>
>>
>>
>> It should be noted that we needed to do something very similar in
>> mainstream MPLS via the synonymous label work which is already adopted.
>>
>> However SL did not address the SR case.. We therefore need this path
>> label work to be progressed.
>>
>>
>>
>> - Stewart
>>
>>
>>
>> On 10/02/2019 08:11, Loa Andersson wrote:
>>
>> > Working Group,
>>
>> >
>>
>> > I have reviewed draft-cheng-spring-mpls-path-segment and as far as I
>>
>> > can see, it is ready for wg adoption.
>>
>> >
>>
>> > There were some comments in Bangkok, but due to the many collisions
>>
>> > between working groups at that meeting I couldn't attend the SPRING
>>
>> > f2f.
>>
>> >
>>
>> > The minutes are not clear, but as far as I understand, there is
>>
>> > nothing that can't be resolved in the wg process.
>>
>> >
>>
>> > /Loa
>>
>>
>>
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